1. Field of the Invention
The present invention relates to a device that can connect a lens to another part of an eyewear, such as a bridge or a temple of a normal spectacle frame with or without rim, or an arm/bridge of a auxiliary spectacle without a temple, with or without rim, for clipping onto a normal spectacle to form a sunglasses or other similar auxiliary function.
2. Description of Related Art
There are many different kinds of lens connection devices to connect a pair of lens onto a bridge and two temples to form mostly a conventional rimless spectacle. A connection device must satisfy three conditions to become a usable lens connection device.
a) There is no relative movement between the connector and the lens.
b) There is no relative rotational movement between the connector and the lens.
c) Because the connection device located on the front of the spectacle, so for esthetic reason, the connector device has to be small in volume and occupy minimal area on the lens.
To fulfill the above conditions a) and b), the convention lens connection devices use two kinds of “Fixing methods”.
Fixing Method A) Two Points Fixing:
The connection device has two fixing points at an interval, each point comprises a bolt or a pin engaged a hole in the lens and fixed by a nut to tighten on one side of the lens, or by a resilient bush being pressed into the gap between the pin and the lens hole, so that the head of the bolt or the flat surface of the nut abutting with the lens surface for the first case. The resilient force of the bush holding the pin against the inner wall of the lens hole for the second case can prevent relative movement but cannot prevent rotation. The second fixing point then only need to prevent rotational movement and may be the same structure as the first fixing point, such as U.S. Pat. No. 7,182,458, U.S. Pat. No. 5,450,141 and FR 2,880,138 or may be a point of contact between a pin on the connector and a slot at the lens edge near the first fixing point, such as the embodiment shown in FIG. 6 of U.S. Pat. No. 6,170,950, or may be a contact surface between a bracket on the connector that touch on the edge of the lens near the first point, such as the embodiment shown in FIGS. 19 and 20 of the '950 patent.
Fixing Method B) One Point Fixing:
This is an improved version of Method A) by eliminating the second fixing point of Method A) and using a non-circular plug on the connector to engage a non-circular orifice in the lens and to form a “form locking joint” to prevent relative rotation. When a direct contact is formed between the plug and the inner wall of the orifice, the joint is referred to as a “Direct Contact Form Locking Joint”, such as EP 1,024,390 and WO 03/050595.
However, in the above two cases and in many other similar cases of the conventional lens connectors, which use a direct contact form locking joint, the joints are 100% in clearance or transitional fit but not in interference fit. Due to the fact of that the connecting hole production method now available is invariable the rotary cutting method, the inherent of this traditional production process (thin and overhanging cutter, feeding direction perpendicular to overhanging length, so generate big bending force) limit the capabilities of copying the plug's shape accurately. Such a mismatch in form between the connecting hole and the plug will cause lens crack unless enough tolerance is left between them. Therefore, the conventional connectors all adopt a Clearance Fit, or at best, a Transitional Fit. These kinds of fits do not have a surface contact and only have a line or point contact or clearance between the plug and the inner wall of the orifice, and this gives rise to relative movement or “shaking” between the plug and the lens.
To solve this shaking problem, there is another kind of form locking joint, which is same as the “direct contact form locking joint”, except that a clearance between the connecting hole and the plug is deliberately maintained, a bush made of resilient material, and has the shape as the clearance but bigger, is forced in to fill up the clearance. The deformation of the resilient bush will exert a force to hold the plug firmly inside the connecting hole. This kind of joint will be refereed to as the Resilient Contact Form Locking Joint, such as US 2003/0076476, U.S. Pat. No. 5,659,380 and U.S. Pat. No. 5,450,141.
However, the conventional lens connectors of the “two points fixing” has disadvantages comparing to the “one point fixing” as follows: occupying bigger area on the lens and being more difficult to manufacture and to assemble because the two points has a separation which needs to match with the corresponding separation of the two pins on the connector.
The conventional “one point fixing” lens connectors, while being superior to the two points fixing, however, has the disadvantage of that the “resilient contact form locking” joint occupies big volume and lens area to cause the eyewear look ugly.
From the above analysis, the last kind of conventional joint, namely: the “one point fixing, direct contact form locking joint” seems to be the best one by the aforementioned three criteria, but it still has two shortcomings due to the limitation of the connecting hole production by the conventional rotary cutting methods, such as drilling followed by end milling using an end milling cutter or followed by grinding or milling using a circular grinding disc or a circular milling cutter, etc. In fact, all of the conventional lens connectors are using rotary cutting to cut the connecting hole, so all of the conventional lens connectors, either they are too bulky, such as the “two point fixing” or “one point fixing resilient contacting form locking” versions. The “one point fixing direct contact form locking” of conventional connector seems to be the best of all, but still has two shortcomings due to the limitation of the rotary cutting method to produce the connecting hole. If theses two shortcomings can be resolved, this “one point fixing direct contact form locking” connector may be the best one as judged by the aforementioned three criteria.
Three cases of the conventional “one point fixing, direct contact form locking” lens connectors are cited below to illustrate what the two shortcomings are.
In the EP '390 patent, the connecting hole is cut by drilling a hole through the lens, then use a circular disc cutter to cut an arc into the lens surface, so that a cavity is formed in the lens surface with an arc bottom, a rectangular opening and a through hole at the center of the opening passing through the bottom.
In the WO '595 patent, the connecting hole is cut by drilling a hole through the lens, then use a end milling cutter to cut the non circular shape on the lens surface with controlled depth.
In the U.S. '476 patent, the through hole in the lens is non-circular shaped and is cut by the same end milling cutter method as the WO '595 patent except that the cutting is passing through the lens thickness, but not in controlled depth. The above 3 cases and many other existing similar cases, whose connecting holes are produced by rotary cutters, all has the following two limitations.
A) Their connecting holes are still too big compare with the smallest form locking connecting hole (SFLCH), which should be a lens orifice limited only by the strength of the connecting element, but not by the lens orifice production method. The plug or the connecting element cannot be too small, otherwise it will break when in use. In the extreme case of minimum volume, the round segment is to directly fit the bridge or the end piece of a spectacle, (an end piece is a spectacle part that connect the temple to the front) the smallest possible bridge or end piece is 1.4 mm (millimeter) diameter wire. Therefore, an SFLCH should be a round segment with a cavity defined in its inner edge to make it non-circular. For maximum anti-rotational force per unit occupied lens area, the best shape of the cavity should be a rectangle slot with two right angled sharp corners running through the lens thickness, which is the same as the key slot found on a machine shaft and the driven wheel thereof. To maintain the circular shape of the round segment, the width of the slot cannot be bigger than 25% of the diameter of the round segment or 0.35 mm. To increase its anti-rotational strength and the aesthetic look, two such slots are formed respectively at the ends of the diameter of the round segment.
Therefore, a smallest form locking connecting hole (SFLCH) as derived from first principle comprises of a round segment defined through the lens and has an inner edge and a diameter of 1.4 mm. A cavity in a rectangular slot form 0.35 mm wide with right angled sharp corners flat bottom is formed in the inner edge of the round segment at each end of the diameter of the round segment, and running through the lens thickness to make the orifice non-circular.
The conventional rotary cutting method cannot produce such a SFLCH, because sharp corner cannot be formed, and the 0.35 mm width slot cannot be formed because that the smallest possible end milling cutter is of 0.8 mm diameter.
B) The conventional method to copy the cross sectional shape of the plug in the connecting hole is by programming the machining path to trace the shape of the plug, but serious error will occur due to 1) the actual shape of the plug deviated from the theoretically programmed shape, and 2) The machine error due to cutter bending etc will not make the shape of the connecting hole being the same as the programmed path. As a result, the connecting hole and the corresponding plug for all the above three cases and many other existing similar cases whose connecting holes are produced by rotary cutting, must be in transitional fit but cannot be in interference fit because the latter require that a precisely controlled amount of interference, and an exact conformity of shape to the cross section of the plug must be maintain when producing the connecting hole to avoid lens crack. However, such a loose fitting has only line or point contact between the plug and the inner wall of the orifice, this cannot lock against shaking. The solution to such shaking by the conventional lens connectors are using a clamping force generated by a bolt and nut passing through the lens's to exert on the two sides of the lens through one abutting surfaces on each side. However, the shake resistant force is the frictional force, which is only a fraction of the clamping force, stronger frictional force require bigger clamping force that may damage the lens, and the abutting surface itself will occupy lens area and affect the aesthetic appearance.
A rimless spectacle, as shown in FIG. 5, comprises two lenses 90, two temples 70, a nose bridge 80 and multiple connectors. Each lens 90 has two through holes 91 defined through the lens 90 respectively near two sides of the lens 90. The temples 70 and the nose bridge 80 are connected to the through holes 91 in the lenses 90 with the connectors. Each connector comprises a threaded rod 71,81 and a nut 72,82. The threaded rod 71,81 is securely attached to one of the temples 70 and nose bridge 80 and is mounted through a corresponding one of the through holes 91 in the lenses 90. The nut 72,82 is securely screwed with the threaded rod 71,81 and abuts against the lens 90 so as to securely connect the temple 70 or nose bridge 80 with the lens 90.
In an alternative embodiment as shown in FIG. 6, another conventional connector may comprise a resilient base 73 held in one of the through holes 91 and an inserting rod 71A formed on one of the temples 70A and the nose bridge and plugged into the resilient base 73. With the engagement between the inserting rod 71A and the resilient base 73, the temples 70A and nose bridge are connected securely with the lenses 90.
However, the conventional connectors shown in FIGS. 5 and 6 cannot prevent the temples 70,70A or nose bridge 80 from rotating relative to the lenses 90, the combination angle between the temples 70,70A or nose bridge 80 with the lenses 90 easily changes.
With reference to FIG. 7, another conventional connector is provided and comprises a threaded rod 71B, a nut 72B and a positioning rod 74. With the arrangement of the positioning rod 74, the temples 70B or nose bridge can be kept from rotating relative to the lens 90B, but a notch 92 should be formed in an edge of the lens 90B.
With reference to FIG. 8, an alternative embodiment of conventional connector may comprise two inserting rods 71C and a resilient connecting base 73C with two holes engaging respectively the inserting rods 71C.
However, the conventional connectors shown in FIGS. 7 and 8 have the following disadvantages.
1. Two through holes 91 or one through hole 91 with one notch 92 have to be formed in each side of the lens 90B,90C for combining with the temple 70B,70C or nose bridge, this takes a large space for defining the holes 91 or notch 92 in the lens 90B,90C.
2. The positions of the rods 71B,71C,74 have to be precisely aligned with the through holes 91 and notch 92, otherwise the temples 70B,70C or nose bridge cannot be connected to the lens 90B,90C.
With reference to FIGS. 9 and 10, a further conventional connector (EP1024390A1) comprises a threaded rod 71D and two positioning ribs 712 formed on two sides of the threaded rod 71D. A positioning groove 912 is defined in the lens 90 and communicates with the through hole 91 to correspond to the positioning ribs 712 on the threaded rod 71D. With the engagement between the positioning groove 912 and ribs 712, the temple 70D or nose bridge can be kept from rotating relative to the lens 90D.
However, the conventional connector shown in FIGS. 9 and 10 has the following shortcomings.
1. The height of the positioning ribs 712 and the depth of the positioning groove 912 should be large and deep enough, otherwise the engaging effect between the groove 912 and ribs 712 will lose. However, this will occupy larger lens area, and cause the volume of the lens 90D enlarged.
2. The shape of the positioning groove 912 in the lens 90D have to be precisely corresponding to that of the ribs 712, any mismatch will cause shaking or lens crack. As aforementioned, such a precise shape and size matching requirement on the groove is difficult to achieve by conventional rotary cutting method, and this causes difficulty for assembling a spectacle.
To overcome the shortcomings, the present invention tends to provide a method for assembling a spectacle to mitigate or obviate the aforementioned problems.